This invention relates generally to spring units for use in mattresses, spring upholstered furniture and the like and, more particularly, to an improved pocketed coil spring unit and associated method of manufacturing such a spring unit.
A well known type of spring assembly includes a number of discrete coil springs, each of which is enclosed in a fabric pocket in a length of folded fabric material. Longitudinal axes of the spring coils are generally parallel with one another so that the top and bottom end turns of the coil springs define top and bottom faces of the spring unit. A spring assembly can be fabricated from such a spring unit by forming rows of the pocketed coil springs and binding or adhering the individual rows together to form a mattress or spring assembly.
This type of spring assembly is commonly referred to as a pocketed spring unit due to the fact that each spring is contained within an individual pocket of fabric material. The construction of strings of pocketed coil springs in each pocket is well known in the art and, for example, disclosed in U.S. Pat. No. 4,439,977 which is hereby incorporated by reference in its entirety. The system disclosed in that patent includes a spring coiler which forms a coil spring which is subsequently compressed and inserted between the plies of folded pocketing fabric material. Other systems for manufacturing pocketed coil spring assemblies are disclosed in PCT Patent Application No. WO94/18116 and U.S. patent application Ser. No. 08/927,051 filed Sep. 10, 1997, each of which are expressly incorporated herein by reference.
Pocketed spring units are generally recognized to have a unique and particular luxurious feel to them and mattresses manufactured of such pocketed spring units provide a feeling of softness without lacking spring resilience or support. Mattresses and similar articles constructed of pocketed spring units are often considered a high-end type of product because of the added benefits and features of the pocketed coil springs. Mattresses and the like of this type can be more costly to manufacture and assemble as a result of the considerable amount of time and labor which is involved in their manufacture, together with the fact that the method of fabrication and assembly of such pocketed spring units can be complicated, particularly in an automated process.
While known systems provide an automated method for producing and assembling pocketed spring units, the increased cost of materials and associated components for mattresses and other items incorporating such spring units can be a detriment to the commercial success of these products, even though they do provide enhanced softness and support as previously described.
Therefore, there is a need for an improved pocketed spring unit and associated method of manufacture which offers all the advantages of known pocketed spring units without the associated higher manufacturing costs and related disadvantages of known pocketed spring units.